The Effects of Various Postemergence Herbicides On the Establishment Rate of Selected Experimental Interspecific Hybrid Bermudagrasses.

Bermudagrass (Cynodon spp.) is the most desirable turfgrass for golf courses and other turfgrass areas in Oklahoma. Bermudagrass is widely used because it is aggressive, has good drought tolerance and is resistant or tolerant to many biotic pests. Bermudagrass is commonly propagated vegetatively through sodding, sprigging, or plugging. A high establishment rate is very important for turfgrass managers to utilize the area quickly and to regulate weed population in the area. The objective of this study was to evaluate the effects of various postemergence herbicides on the establishment rate of selected experimental interspecific hybrid bermudagrasses (Cynodon dactylon x C. transvaalensis) in Oklahoma. This study was conducted in Stillwater, OK at the Oklahoma State University Turfgrass Research Center. Three experimental interspecific hybrid bermudagrasses (OKC 1119, OKC 1134, and OKC 70-18) and one standard cultivar (Tifway) were used for this study. Plots (91 x 91 cm) were established with 5 green house grown plugs (39cm2) on 15 July 2009 with four replications and herbicide treatments were applied at the maximum and double the maximum labeled rate for bermudagrass turf on 29 July 2009. Herbicide treatments were as follows: 1) Untreated control, 2) MSMA at 2.2 kg ai/ha, 3) MSMA at 4.4 kg ai/ha, 4) Quinclorac at 0.8 kg ae/ha, 5) Quinclorac at 1.6 kg ae/ha, 6) Metsulfuron at 0.025 kg ai/ha, and 7) Metsulfuron at 0.050 kg ai/ha. Herbicide phytotoxicity was assessed visually at 1, 2, and 4 weeks after treatment (WAT), and ratings were not significantly different from the untreated control on each rating date. Digital photographs were taken to measure percent bermudagrass coverage at 0, 1, 2, 4, 6, and 8 WAT. There was no significant herbicide x cultivar difference in percent bermudagrass coverage at 0, 1, 2, 4, or 6 WAT. There was a significant herbicide x cultivar difference in percent bermudagrass coverage at 8 WAT where Tifway, OKC 1119, and OKC 1134 were at or near 100% establishment regardless of treatment while OKC 70-18 establishment was significantly reduced in Quinclorac at 1.6 kg ae/ha, Metsulfuron at 0.025 kg ai/ha, and Metsulfuron at 0.050 kg ai/ha treated plots. When compared within a single bermudagrass selection/cultivar, Metsulfuron treatments significantly reduced bermudagrass coverage compared to the untreated control for all bermudagrasses used in this study while Quinclorac treatments significantly reduced bermudagrass coverage of OKC 70-18 only. During this study, the average daily temperatures in Stillwater, OK were below normal and may help to explain why there was no visual evidence of herbicide phytotoxicity in treated plots compared to control plots. This study will be repeated in the summer 2010 for further data collection and analysis.